Tommy Caldwell, top, ascends the final pitch of the Dawn Wall on El Capitan, belayed by his climbing partner Kevin Jorgeson, below, in Yosemite National Park, Calif., Jan. 14, 2015. Using ropes as a safety measure only, Caldwell and Jorgeson became the first to climb by hand the 3,000-foot granite wall, an ascent they began on Dec. 27, 2015. less

Tommy Caldwell, top, ascends the final pitch of the Dawn Wall on El Capitan, belayed by his climbing partner Kevin Jorgeson, below, in Yosemite National Park, Calif., Jan. 14, 2015. Using ropes as a safety ... more

Photo: MAX WHITTAKER / New York Times

Photo: MAX WHITTAKER / New York Times

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Tommy Caldwell, top, ascends the final pitch of the Dawn Wall on El Capitan, belayed by his climbing partner Kevin Jorgeson, below, in Yosemite National Park, Calif., Jan. 14, 2015. Using ropes as a safety measure only, Caldwell and Jorgeson became the first to climb by hand the 3,000-foot granite wall, an ascent they began on Dec. 27, 2015. less

Tommy Caldwell, top, ascends the final pitch of the Dawn Wall on El Capitan, belayed by his climbing partner Kevin Jorgeson, below, in Yosemite National Park, Calif., Jan. 14, 2015. Using ropes as a safety ... more

If anyone can speak to the visceral effects of climate change on Yosemite National Park, it is record-setting climber Tommy Caldwell.

Caldwell is the subject of "The Dawn Wall," a new documentary that chronicles the 19 treacherous days he and Kevin Jorgeson ascended the Dawn Wall of El Capitan in Yosemite. The climb is considered one of the trickiest in the world, and Caldwell and Jorgeson were the first to successfully free climb it.

Caldwell has been setting climbing records in Yosemite for nearly two decades, and in that time he says he's noticed disturbing changes in the national park, changes he (and numerous scientists) attributes to climate change.

"I still consider Yosemite valley one of the most beautiful places in earth," he wrote in a recent Instagram post. "But the effects of climate change here are shocking."

Caldwell also describes how the "good climbing season shifted by at least a month and snow rarely blankets the valley floor any more."

He relates his observations of Yosemite to the bigger picture of climate change, writing, "It doesn't take much research to understand that symptoms like this at home are only the start."

"Everyone wants to find something to care deeply about," he writes to his 342,000 Instagram followers. "Maybe we should consider letting the threats to the survival of our planet and our fellow humans bring us to life."

"The Dawn Wall," directed by Josh Lowell and Peter Mortimer, was released in theaters nationwide on September 19. It is currently available to rent on streaming services.